1. Field of the Invention
The present invention relates to a photographic light-sensitive sheet for the color diffusion transfer process and, more particularly, to a silver halide photographic light-sensitive sheet for the color diffusion transfer process containing a novel dye releasing redox compound.
2. Description of the Prior Art
Color diffusion transfer color image forming processes using a dye releasing redox compound are described in U.S. Pat. Nos. 3,928,312, 3,931,144, 3,942,987, 3,932,381 and 3,954,476, U.S. patent application Ser. No. 439,809, Japanese Patent Application (OPI) No. 104343/1976 and Research Disclosure, Vol. 130, No. 13024 (February, 1975). The term "dye releasing redox compound" herein means a compound containing therein a group referred to as a redox moiety and a dye or a dye precursor moiety. The redox moiety renders the redox compound immobile due to the presence of a ballast group attached thereto, but under alkaline conditions the compound splits and releases a compound containing the dye moiety (a dye compound). For instance, when a light-sensitive element having a light-sensitive silver halide emulsion layer and a dye-releasing redox compound associated therewith is exposed and developed with an alkaline processing solution, the redox moiety per se is oxidized in proportion to the amount of developed silver halide and the compound splits into a dye compound and a non-diffusible quinone compound. As a result, the dye compound diffuses into an image-receiving layer to provide a transferred image therein.
Examples of dye-releasing redox compounds which release yellow dyes are described in U.S. Pat. No. 3,928,312 and Research Disclosure, Vol. 130, No. 13024 (February, 1975), etc. However, technical problems are encountered, using the dye releasing redox compounds specifically described in such prior art, in that the transferred images have insufficient stability. For example, the light fastness of the images is not good and the images fade to a large extent in a light place. Also, the transfer of the dye compound is not adequate (i.e. the transfer speed is inferior).
Further, improved yellow dye releasing redox compounds are described in U.S. Pat. No. 4,013,633. However, further investigation has revealed that the color hue of dye compounds released from the yellow dye releasing redox compounds described above changes to a large extent with pH, and that the mordantability and transferability of the dye compounds are insufficient.